The vote was a major victory for environmentalists, with many openly hoping to leverage the issue to hasten Diablo Canyon's demise. The powerful commission oversees the state's 1,100-mile coastline, and the board and staff agreed the proposal, which already won approval from the State Lands Commission, didn't meet stringent coastal rules.

Says Blair Jones, PG&E spokesperson: “PG&E put forth a sound and comprehensive plan to conduct this research, which was guided by seismic experts, state and federal agencies and our commitment to performing the work in an environmentally responsible manner. While we are disappointed with the decision, we appreciate the work of the Commission staff and members in considering this seismic study proposal. We will focus on gathering and interpreting this recently collected data as we evaluate the Commission’s decision to determine how to proceed with additional seismic data collection efforts.”